Engine

ABSTRACT

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application is a continuation of U.S. patent applicationSer. No. 13/242,229, filed Sep. 23, 2011, which claims priority to U.S.Provisional Application Ser. No. 61/385,802, filed Sep. 23, 2010, thecomplete disclosures of which are expressly incorporated by reference.

FIELD OF THE DISCLOSURE

The subject disclosure relates to engines, in particular to engines foruse in powersports equipment.

Multiple different engine types are known, for example, multiple fueltypes are available, and multiple different sized engines are available,together with different numbers of cylinders. Engines may also be 2 or 4stroke, and be positioned at multiple different orientations, forexample the piston(s) may be oriented vertically, horizontally, or atany other possible orientation. The subject disclosure is applicable toall types of such engines.

SUMMARY

In a first embodiment, an engine comprises a crankcase, a crankshaftjournalled in the crankcase, a piston coupled to the crankshaft, acylinder in which the piston reciprocates, and a head positioned overthe piston and cylinder. The crankcase is split along a plane formingfirst and second crankcase portions, with fluid passages being in onlythe first crankcase portion, the fluid passages communicating with thehead to deliver fluid to the head.

The above mentioned and other features of this invention, and the mannerof attaining them, will become more apparent and the invention itselfwill be better understood by reference to the following description ofembodiments of the invention taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an upper perspective view of the subject engine;

FIG. 2 is an upper perspective view of the opposite side of the engineas that shown in FIG. 1;

FIG. 3 is a lower perspective view similar to that of FIG. 1;

FIG. 4 is a lower perspective view similar to that of FIG. 2;

FIG. 5 shows an exploded view of multiple components of the engine takenfrom the perspective shown in FIG. 2;

FIG. 6 shows the split housing portions of the crankcase;

FIGS. 7 and 8 are the opposite sides of the crankcase portions as shownin FIG. 6;

FIG. 9 is a cross-sectional view taken through lines 9-9 of FIG. 6;

FIG. 10 is a cross-sectional view taken through lines 10-10 of FIG. 6;

FIG. 11 is a perspective view of the crankcase partially broken away toshow a cooling water passage;

FIG. 11A is an enlarged view of the portion denoted in FIG. 11;

FIG. 12 is a cross-sectional view taken through lines 12-12 of FIG. 6;

FIG. 13 is a perspective view of the crankshaft and connecting rodassembly;

FIG. 14 is a cross-sectional view through lines 14-14 of FIG. 13;

FIG. 15 is an exploded view of the assembly shown in FIG. 13;

FIG. 16 is an exploded view of the connecting rod and piston assembly;

FIG. 17 is a cross-sectional view of the piston and connecting rod ofFIG. 16 in an assembled configuration;

FIG. 18A is an underside perspective view of the cylinder liner;

FIG. 18B is an top perspective view of the cylinder liner;

FIG. 19 is a cross-sectional view through lines 19-19 of FIG. 18A;

FIG. 20A is an underside perspective view of the head assembly;

FIG. 20B is an upper perspective view of the head assembly;

FIG. 21 is a cross-sectional view through lines 21-21 of FIG. 20A;

FIG. 22 is a cross-sectional view through lines 22-22 of FIG. 20A;

FIG. 23 is a cross-sectional view through lines 23-23 of FIG. 20A;

FIG. 24 is a perspective view of the cam shaft retainer;

FIG. 25 is a cross-sectional view through lines 25-25 of FIG. 24;

FIG. 26 is a perspective view showing the crankshaft and counter-balanceshaft in an assembled condition in one of the crankcase portions;

FIG. 27 shows the drive train assembly between the crankshaft and thedouble overhead cams;

FIG. 28 shows an exploded view of the oil pump assembly;

FIG. 29 shows the oil pump assembly of FIG. 28 in an assembledcondition;

FIG. 30 shows an exploded view of the water pump assembly;

FIG. 31A shows an exploded view of the water pump housing with thestator poised for attachment thereto;

FIG. 31B shows an assembled view of the water pump housing and stator;

FIG. 32 shows the rotor poised for attachment to the crankshaft;

FIG. 33 shows the gear train of the starter assembly;

FIG. 34 shows an alternate view of the gear train for the starter motor;

FIG. 35 is a cross-sectional view through lines 35-35 of FIG. 4;

FIG. 36 is a cross-sectional view through lines 36-36 of FIG. 4;

FIG. 37 is a cross-sectional view through lines 37-37 of FIG. 1;

FIG. 38 is an enlarged cross-sectional view similar to that of FIG. 37showing the oil distribution pattern;

FIG. 39 is a cross-sectional view through lines 39-39 of FIG. 37;

FIG. 40 shows a cross sectional view through the liner, showing thefluid flow patterns;

FIG. 41 is an exploded view showing the head assembly and cylinder linerpoised for assembly, and showing the fluid flow patterns;

FIG. 42 shows a perspective view of the engine showing a waterdistribution pattern;

FIG. 43 is a cross-sectional view through lines 43-43 of FIG. 1;

FIG. 44 is a cross-sectional view through lines 44-44 of FIG. 1;

FIG. 45 is a perspective view of the counterbalance shaft;

FIG. 46 is a front view of the counterbalance shaft of FIG. 45;

FIG. 47 shows a perspective view of the drive gear of the counterbalanceshaft;

FIG. 48 shows an exploded view of the shaft of FIG. 47;

FIG. 49 shows an outside view of the backlash gear;

FIG. 50 shows an inside view of the backlash gear;

FIG. 51 is a side view of the crankcase assembly;

FIG. 52 is a cross-sectional view through lines 52-52 of FIG. 51; and

FIG. 53 shows a detail view of the oil pickup.

DETAILED DESCRIPTION OF THE DRAWINGS

As best shown in FIGS. 1-4, the engine of the subject disclosure isshown generally at 2, and generally comprises the components of acrankcase 4, a cylinder liner 6, a head assembly 8, a valve cover 10,and a crankshaft assembly 12. As shown, crankcase 4 is comprised offirst and second portions 18, 20, a water pump assembly 24, an oilfilter 26 and a starter motor 30. As shown in FIG. 5, water pumpassembly 24 includes a water pump housing 36 and a water pump cover 38,together with gaskets 40 and 42 as described herein. As also shown inFIG. 5 engine 2 further comprises, a liner gasket 46, a head gasket 48,and a valve cover gasket 50. With reference now to FIGS. 6-12, thecrankcase 4 will be described in greater detail.

With respect first to FIGS. 6 and 8, first crankcase portion 18 iscomprised of a planar surface 60 which defines a split line of thecrankcase assembly along a vertical plane. As should be appreciated,surface 60 defines a flange face having a plurality of bosses havingthrough holes at 62 as described herein. First crankcase portion 18 alsoincludes a top face 66 which produces a planar surface for receivingcylinder liner 6 as described herein. Crankcase portion 18 furtherincludes a main bearing 70 and a roller bearing 72 (for a counterbalanceshaft) as described herein.

It should also be understood from the specification that suchorientational descriptions, such as the term “vertical”, is forreference only as viewed in the disclosed embodiment, and that theengine split line may actually be horizontal, or at some other angle.

As shown best in FIGS. 8 and 11A, crankcase portion 18 also includes anoil pump mounting portion 80 defining a mounting face at 82, and whichis in communication with an oil duct 84 (FIG. 9). Oil duct 84 is furtherin communication with an inlet or snorkel at 86. As shown herein, itshould be appreciated that duct 84 and inlet 86 are integrally cast withthe remainder of the crankcase portion, although it should be understoodthat other components could be provided such as tubes or other suchassemblies. As best shown in FIG. 11A, an oil trough is formed to catcha pool of oil to assist in priming the pump.

With reference now to FIGS. 9 and 10, the integration of the oil pumpinto crankcase portion 18 will be described. As shown in FIG. 9, duct 84and inlet 86 are shown in cross-section which shows the definition of anoil passage way 100 leading into a pump inlet chamber 102. A pump outletchamber 104 discharges into passageway 106 through face 110. As shown inFIG. 10, a further passageway 120 extends from face 110 to a groove 122about an aperture 124. Note that bearing 70 (FIG. 8) is profiled to bepositioned in aperture 124. A final passageway 126 extends frompassageway 120 to top surface 66, which is in communication with aserpentine slot 128 (see FIG. 8).

With reference again to FIG. 8, the exterior of crankcase portion 18 isprovided with a wall 130 which circumscribes bearings 70, 72 and oilpump mount 80. Wall 130 defines a cavity 132 having a front face at 134having a groove 136 and a plurality of bosses having threaded apertures138. It should be appreciated that face 134 defines a mounting face forwater pump assembly 24 as further described herein. Crankcase portion 18further includes a mounting wall 140 for starter motor 30, as describedherein, and an access opening 142, and mounting aperture 144.

With reference to FIGS. 8 and 11, a water input passageway is providedat 150 which extends from mounting face 134 and communicates withchannel 152 which opens onto top face 66. With reference to FIGS. 8 and12, crankcase portion 18 includes a semi-cylindrical opening at 160(FIG. 8) and a channel at 162. As shown best in FIG. 12, channel 162opens into cavity 132 and is aligned with aperture 124 as describedherein.

With reference now to FIGS. 6 and 7, crankcase housing portion 20generally includes a mounting face at 200 having bosses with threadedopenings at 202. It should be appreciated that each of the threadedopenings 202 is aligned with the openings 62 and that mating face 200 isa mirror image of mating face 60 of crankcase portion 18. Crankcaseportion 20 also includes an upper face 206 which is planar with upperface 66 of crankcase portion 18. Crankcase portion 20 includes a rollerbearing 210 longitudinally aligned and opposite bearing 70, and a rollerbearing 212 longitudinally aligned and opposite roller bearing 72.Finally, crankcase portion 20 includes a semi-cylindrical opening 220which together with semi-cylindrical opening 160 defines a cylindricalopening for cylinder liner 6 as described herein. It should beappreciated from the above description that all of the crankcase oil andwater passages are provided in crankcase portion 18, and that none ofthe passages are provided in crankcase portion 20.

With reference now to FIGS. 13-15, crankshaft assembly 12 will bedescribed in greater detail. As shown in FIGS. 13 and 15, crankshaftsubassembly is comprised of a first crank portion 260, second crankportion 262, where the two crank portions are coupled together by way ofan intermediate press-fit pin 264 (FIGS. 14 and 15). As shown in FIG.14, crank portion 260 includes a shaft first end 266 having a diameterportion 268, diameter 270, keyway 272, and water pump drive 274 profiledwith a groove 276. A cam chain gear 278 is integrally provided betweendiameters 268, 270, and a drive gear 280 is provided on shaft diameter282 (FIG. 15). First crank portion 260 is further provided by firstoffset portion 284 having aperture 286, and counterweight portion 288.In a similar manner, crank portion 262 is provided with a shaft secondend 290 having a second offset portion 294 having aperture 296 andcounterweight 298.

As shown in FIG. 15, connecting rod 265 includes a first end 300 havingaperture 302, and second end 304 having aperture 306. It should beappreciated that split bearing 310 is received in aperture 302 and overpin 264. As shown in FIG. 15, a sleeve bushing 312 is provided, which ispositioned in aperture 306 as described herein.

As shown best in FIG. 14, first end 266 includes a longitudinallyextending oil passageway 320 having a passageway 322 communicating withsurface 268, passageway 324 communicating with surface 270 andpassageway 330 which communicates with aperture 286. Pin 264 includespassageway 340 which aligns with passageway 330 and opens into internalvolume 342 of pin 264. Pin 264 includes end caps 344 to close theinternal volume 342. Pin 264 further includes passageway 350 (see FIG.15) which is positioned between the offset portions 284, 294 of crankportions 260, 262, which as should be appreciated, is aligned with splitbearing 310.

With reference again to FIGS. 14 and 15, sleeve bearing 312 is comprisedof grooves 360 and markings in the form of notches 362. As best shown inFIG. 14, both sleeve 312 and connecting rod second end 304 are taperedsuch that the sleeve has a narrow top portion 364 (FIG. 15) and awidened lower portion 366. In a similar manner, connecting rod secondend 304 has a narrow top portion 370 and a widened lower portion 372(FIG. 14). Markings allow one to see the alignment of the sleeve bearingrelative to the connecting rod during assembly, and as the markings areslots, allows the facilitation of the rotational positioning of thebushing. That is a tool can grip the notches 362 and assure that thesleeve bearing is inserted in its proper rotational orientation.

With reference now to FIGS. 16 and 17, piston 390 is shown having aplurality of piston rings 392 provided in complementary grooves 394 asis known by those skilled in the art. Piston 390 further includesintegral support areas 400 providing apertures 402 for receiving pin404. As is also known in the art, snap rings 406 are provided which arereceived in complementary grooves 408 for retaining the pin 404 inposition. As best shown in FIG. 17, support portions 400 define taperedsurfaces 410, tapering inwardly and upwardly in order to provide acomplementary receiving opening 412 to receive second end 304 ofconnecting rod 265. The reduced mass of the connecting rod 265 (by wayof the tapered end 304) allows extra mass to be added to the piston tostructurally rigidify the piston upper end, for example, at the upperend at the positions shown at 414.

With reference now to FIGS. 18A and 18B, cylinder liner 6 will bedescribed in greater detail. As shown, cylinder liner 6 includes anupper portion 440 and an extension portion 442 which define a cylinderwall 444 as described herein. Upper portion 440 includes an uppersurface 450 (FIG. 18B) and a lower surface 452 (FIG. 18A). An extension454 is provided defining a chain receiving channel 456 therein. As shownin FIG. 18A, lower surface 452 has a water inlet opening at 460 whichopens into channel 462 (FIG. 18B) which encircles cylinder wall 444. Anoil passageway 470 also extends between lower surface 452 (FIG. 18A) toupper surface 450 (FIG. 18B). Groove 472 (FIG. 18A) is also providedwhich communicates with opening 474. As shown best in FIG. 19, aperture474 communicates with passageway 476 which in turn communicates withpassageway 478 of injector 480. Injector 480 includes an injector nozzle482 as described herein. Apertures 486, in addition to aperture 474, areused to interconnect cylinder liner 6 with crankcase 4 as furtherdescribed herein. Liner 6 also includes coupling 490 which communicateswith channel 456 and receives injector 480 as best shown in FIG. 19.

As shown in FIG. 20A, head assembly 8 includes a lower surface at 500and an upper surface 502 as shown in FIG. 20B. A plurality of waterinlet slots 504 are provided which encircle valves 506 (exhaust valves506A and air inlet valves 506B) and which open into a cavity 510 (seeFIG. 21). Cavity 510 encircles the head assembly 8 and is incommunication with a water outlet at 512. As shown best in FIG. 20A, anoil inlet aperture is provided at 520 which extends between lowersurface 500 and upper surface 502 as shown in FIG. 20B. Apertures 530(FIG. 20A) are provided for mounting head assembly 8 to liner 6, butapertures do not extend through the top surface 502 of head assembly 8,but rather terminate internally of head assembly 8, for example as shownbest in FIG. 22, where a machined top surface 532 is provided to receivefasteners such as washers and fastening nuts, as further describedherein.

As shown in FIG. 20A, an exhaust port 540 is provided opposite exhaustvalves 506A, and as shown in FIG. 20B, an air intake port 546 isprovided opposite intake valves 506B (FIG. 20A). A chain receivingchannel 550 is also provided which, aligns with channel 456 (FIG. 18B).Channel 550 is defined in part by wall 560 (FIG. 20B) having mountingapertures at 562 and 564. An intermediate wall 570 is provided havingmounting apertures 572 and 574. Walls 560 and 570 also includesemi-cylindrical surfaces 580, 582, 584, and 586. It should beappreciated that the receiving areas 580 and 584 receive the overheadcam for the air intake valves and the receiving areas 582 and 586receive the overhead cam for the exhaust valves.

With reference now to FIGS. 24 and 25, a cam retainer 600 is shown. Asshown best in FIG. 25, cam retainer 600 includes semi-cylindrical areas610, 612, 614, and 616, which as should be appreciated overlapssemi-cylindrical receiving areas 580, 582, 584, and 586, (FIG. 20B)respectively, to define a cylindrical receiving area for encapsulatingoverhead cams, as further described herein.

As shown in FIGS. 24 and 25, cam retainer 600 also includes apertures622 which align with apertures 562 (FIG. 20B); apertures 624 which alignwith apertures 564 (FIG. 20B); apertures 626 which align with apertures572 and apertures 628 which align with apertures 574 (FIG. 20B). As alsoshown, retainer 600 includes a channel 630 which aligns with aperture520 (FIG. 20B) and is in fluid communication with groove 632 whichextends around receiving area 612. Channel 632 communicates with achannel 634 by way of passageway 636. Channel 638 communicates withchannel 634 by way of a passageway 640. Passageway 642 communicates withpassageway 632 in a similar manner as passageway 640, although notshown.

With reference now to FIG. 26, multiple subassemblies will now bedescribed. With reference first to FIG. 26, crankshaft subassembly 12 isshown mounted within crankcase portion 20 along with a counterbalanceshaft 700. Counterbalance shaft 700 includes gear 702 in meshingengagement with gear 280 on crankshaft subassembly, and further includescounterweight 704, shaft 706 positioned in roller bearing 212, a bearingportion 708 and a drive portion 710. As shown, shaft 706 has a squarecross section to increase the stiffness and reduce the deflection.

With reference now to FIG. 27, crankshaft subassembly 12 andcounterbalance shaft 700 are shown in meshing engagement, together withcam chain 720 in meshing engagement with gear 278. Cam chain 720 is inmeshing engagement with upper gears 722 and 724; where gear 722 drivesexhaust cam 726 and where gear 724 drives air intake cam 728. Retainers730 and 732 are shown which keep the chain at the proper tension as wellas insure that the chain is wrapped around the associated gears.Injector 480 is also shown (see also FIG. 18A) which provideslubrication to the retainer and to chain 720, as discussed above.

With reference now to FIG. 28, an oil pump assembly 750 is shown poisedfor receipt within oil pump mounting portion 80 of crankcase portion 18.As shown in FIG. 28, the drive end 710 (of counterbalance shaft 700) anddrive end 274 (of crankshaft assembly 12) protrude through crankcaseportion 18 and are positioned within cavity 132. A seal 752 ispositioned over bearing 72 and sprocket 754 is positioned over drive end710 and fixed in place by a fastener such as 756.

Oil pump assembly 750 is comprised of outer rotor 760, inner rotor 762,pump shaft 764 having cross pin 766 and pump housing 770. It should beappreciated that outer rotor 760 may be positioned within inner diameter772 of mounting portion 80. Inner rotor 762 is also positioned withinouter rotor 760 and shaft 764 is positioned in opening 774. Housing 770is interconnected to mounting portion 80 by way of fasteners 780. Itshould be appreciated that a portion of shaft 764 extends throughopening 782 of housing 780 and the extending portion has a D-shapedcross section which matches with a complementary opening 790 on sprocket792. Sprocket 792 is held in place by way of fastener 794 threadablyreceived in the end of shaft 764. It should be appreciated that a chainsuch as 800 is entrained around sprockets 754 and 792 to drive innerrotor 762. Thus, it should be appreciated that the inner rotor 762 ofthe oil pump 750 is driven by the rotation of the crankshaft assembly 12through counterbalance shaft 700. The assembled oil pump assembly isshown in FIG. 29 assembled to crankcase portion 18.

With reference now to FIG. 30, water pump assembly 24 is shown includingwater pump housing 36 and water pump cover 38. Water pump assembly 24further includes water pump driveshaft 820, spacer 822, seal 824,impeller 826, and gasket 828. As shown, water pump housing 36 includesan outer side 830 which includes cavity 832 for receiving impeller 826,which is in communication with a discharge duct 840. Duct 840communicates with aperture 842 (FIG. 31A). Water pump cover 38 includesan intake duct 850 which is profiled for receiving a flexible rubberhose and clamp thereover (not shown). Water pump cover 38 is fastened tofront face 830 of water pump housing by way of a plurality of fasteners852. When assembled, impeller 826 is coupled to shaft 820, and shaft 820projects through aperture 844 of pump housing 36 to the position shownin FIG. 31B. It should also be appreciated that shaft 820 has a drivenend in the form of a tongue 846 (FIG. 31A) which, matches groove 276(FIG. 15). It should also be noted that cavity 832 is formed in astepped fashion, so as to allow alternate impeller sizes. This allowsalternate cooling water flow rates for other engine ratings.

With reference now to FIG. 31A through FIG. 32, a magneto assembly willbe described. As shown in FIG. 31A, water pump housing 36 includes aninner face 860, and includes an internal cavity at 862. A stator 864 isprovided and is mounted by way of fasteners 866 to threaded bosses 868within cavity 862. Stator 864 is shown in its mounted condition in FIG.31B. Note that center opening 870 through stator 864 allows access toshaft 820 to drive water pump impeller 826 (FIG. 30). A starter motorgear drive 880 is also shown in FIG. 31A having large drive gear 882 andsmall driven gear 884 coupled about shaft 886. Shaft 886 is received inaperture 888. Gear drive 880 is also shown in its installed condition inFIG. 31B.

With reference now to FIG. 32, the rotor for the magneto assembly isshown at 900 including outer rotor wall 902 profiled to overlap stator864 and having inner opening at 904 profiled to be attached tocrankshaft assembly 12. As shown in FIG. 32, starting gear 910 is shownwhich is received onto diameter portion 268 (FIG. 14) and rotate theretorelative to bearing 912. A slip clutch 920 is provided which is mountedto the inner face 922 of rotor 900 by way of fasteners such as 924.Starter gear 910 includes an external hub 926 which interacts with inneropening 928 of slip clutch 920.

The assembled starter motor gearing is shown in FIGS. 33 and 34 where itis understood that starter motor 30 includes a starter motor shaft 930in the form of a pinion. It should be appreciated that starter motor 30mounts to the back side of mounting wall 140 (FIG. 8), with startingshaft 930 projecting through aperture 142 (FIG. 8). Thus, gears 882 and884 rotate relative to shaft 886 pinned at one side by aperture 888(FIG. 31A) and by mounting aperture 144 (FIG. 8) on the opposite side.With the components and subassemblies as described above, the oil andwater distribution will now be described.

With reference first to FIG. 35, as oil pump 750 (FIG. 28) operates, oilis drawn in the direction of the arrows through passageway 100 to thepump and is discharged into passageway 106. Filter 26 is connected tothe crankcase by way of a mounting bracket 950 having a passageway 952,aligned with passageway 106, and extending into the filter 26. Withreference now to FIG. 36, oil is pumped out of the filter 26 through apassageway 956 of bracket 950 into passageway 120 of crankcase portion18. As mentioned before, passageway 120 intersects with groove 122 whichcorresponds with diameter portion 268 (FIGS. 10 and 14) lubricating themain bearing 70 on the crankshaft portion 268 (FIG. 37). As shown inFIG. 37, aperture 322 also extends through diameter portion 268 (FIG.37), intersecting with passageway 320, and allowing oil from passageway120, 122 (FIG. 36) to enter passageway 320.

As shown best in FIGS. 37-39, oil in passageway 320 flows in bothdirections from passageway 322 (FIG. 38). Oil flowing to the left asviewed in FIG. 39 lubricates the connection between shaft 820 and driveend 274. Bearing 912 (FIG. 39) is also lubricated through passageway324. As shown in FIG. 38, oil flowing to the right continues throughpassageway 330 and into internal volume 342 of pin 264 throughpassageway 340. Oil then lubricates bearing 310 through passageway 350of pin 264 (FIG. 15). Excess oil from bearing 310 simply drips back tothe crankcase sump.

Recall from FIG. 36, that oil through passageway 120 not only fed groove122 around main bearing, but also travels vertically through passageway126, feeding serpentine groove 128 (FIG. 8). A portion of serpentinegroove is seen in FIG. 36. With reference now to FIG. 41, oil throughserpentine groove 128 feeds passageway 470 of liner 6 as well as channel472. The oil through passageway 470 is fed to passageway 520 of headassembly 8, whereas oil through passageway 472 is fed to injector 480through nozzle 482 onto the chain as previously described. Recall alsofrom FIG. 20B that passageway 520 extends upwardly opening onto uppersurface 502 within wall 560. Oil is then fed to channel 630 of camretainer 600, and oil is then fed onto the cams through the variouschannels around cam shafts as previously described.

With respect now to FIG. 42, water from water pump 24 is drawn inthrough hose (not shown) attached to duct 850 and is discharged throughaperture 842 of water pump housing 36. Water exits into crankcaseportion 18 through aperture 150 and then vertically through channel 152.With reference again to FIG. 40, water then progresses through aperture460 of liner 6 and circulates around cavity 462, cooling cylinder wall444. Water then feeds into passageways 504, as shown in FIGS. 41 and 43,into head 8. Cooling water continues to circulate around passageway 510as shown best in FIG. 44 and progresses to a water outlet throughthermostat 980.

With reference now to FIGS. 45-50, counterbalance shaft is shown at 1000including a drive gear 1002, a counterweight 1004, and a shaft 1006. End1008 includes a drive end 1010 in the form of a tongue. Gear 1002 iscomprised of outer gear 1014 and a backlash gear 1012. A plurality ofsprings is positioned intermediate the gears 1012, 1014, to provide atorsional spring load between the gear 1002 and its mating gear. Withrespect now to FIGS. 48 and 50, gear 1014 includes spring receivingrecesses 1018 and gear 1012 includes a corresponding recess 1020 havinga chamfer (FIG. 50) at 1022. Thus the spring will fit between therecesses 1018 the chamfers 1022 such that the gears 1014, 1012 may sitflush to each other, and rotate subject to the spring load.

With reference now to FIG. 1, an exhaust vapor recovery chamber 1050will be described which recirculates the crankcase blow by gases throughvalve 1050 back to the air intake. As shown in FIGS. 51 and 52, breather1050 includes an opening 1054 into the crankcase, as well as baffles1056 and 1058. A drain channel 1060 connects the recovery chamber 1050to the crankcase. Blow by gases from the crankcase make multipledirectional changes as shown by the arrows in FIG. 52 which separatesthe oil from the blow by gases, allowing the oil to drain back throughdrain channel 1060 and allowing the blow by gases to extend upwardlythrough valve 1052 (FIG. 1) which is mounted on upper surface 1062. Theblow by gases are then re-introduced through the valve 1052, through athrottle and back through air intake (546, see FIG. 20B).

Finally with respect to FIG. 53, a pickup filter 1100 is providedpositioned in the crankcase oil sump and connected to snorkel 86, forfiltering oil to the oil pump.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

1. (canceled)
 2. An engine, comprising: a crankcase; a crankshaftjournalled in the crankcase; a piston; a cylinder in which the pistonreciprocates; a head positioned over the piston and the cylinder; and aconnecting rod coupling the piston to the crankshaft, the connecting rodhaving a first end coupled to the crankshaft and a second end coupled tothe piston, the second end being tapered inwardly and upwardly, and thepiston comprising a complementary tapered coupling with a pin couplingthe second end of the connecting rod to the piston.
 3. The engine ofclaim 2, wherein the complementary tapered coupling includes an openingin a lower portion of the piston, and the opening receiving the secondend of the connecting rod.
 4. The engine of claim 3, wherein the openingtapers inwardly and upwardly from the lower portion of the pistontowards an upper portion of the piston.
 5. The engine of claim 4,wherein the upper portion of the piston is wider than the lower portionof the piston, and the opening extends into the upper portion of thepiston.
 6. The engine of claim 2, wherein the second end of theconnecting rod has a lower portion and a top portion, and the lowerportion is wider than the top portion.
 7. The engine of claim 2, whereinthe second end of the connecting rod includes an aperture configured toreceive the pin.
 8. The engine of claim 7, further comprising a bushingpositioned within the aperture of the second end of the connecting rod,and the bushing is positioned intermediate the aperture and the pin. 9.The engine of claim 8, wherein the bushing includes a taperedconfiguration complementary to the configuration of the tapered secondend of the connecting rod.
 10. The engine of claim 9, wherein an upperend of the bushing has a width less than that of a lower end of thebushing.
 11. The engine of claim 2, wherein the crankcase is split alonga plane forming a first crankcase portion and a second crankcaseportion, and fluid passages are provided in only the first crankcaseportion, and the fluid passages communicate with the head to deliverfluid to the head.
 12. An engine, comprising: a crankcase; a crankshaftjournalled in the crankcase; a piston; a cylinder in which the pistonreciprocates; a head positioned over the piston and cylinder; and aconnecting rod coupling the piston to the crankshaft, the connecting rodhaving a first end coupled to the crankshaft and a second end coupled tothe piston, the second end being tapered inwardly and upwardly andconfigured to support a press fit bushing, and the bushing havingmarkings to align the bushing properly within the second end.
 13. Theengine of claim 12, wherein the piston comprises a complementary taperedcoupling configured to receive a pin for coupling the second end of theconnecting rod to the piston.
 14. The engine of claim 13, wherein thebushing is positioned intermediate the pin and the second end of theconnecting rod.
 15. The engine of claim 13, wherein bushing has a widthless than that of the pin.
 16. The engine of claim 15, wherein thebushing includes an upper end and a lower end, and a width of at leastone of the upper end and the lower end is less than the width of thepin.
 17. The engine of claim 16, wherein the width of both the upper endand the lower end of the bushing is less than the width of the pin. 18.The engine of claim 12, wherein the markings are slots configurated forrotational positioning of the bushing with respect to the second end ofthe connecting rod.
 19. The engine of claim 12, wherein the second endof the connecting rod includes an aperture configured to receive thebushing.
 20. The engine of claim 19, wherein the bushing axially extendsfrom a first end to a second end, and the first end of the bushing isaligned with a first side of the second end of the connecting rod andthe second end of the bushing is aligned with a second side of thesecond end of the connecting rod.
 21. The engine of claim 12, whereinthe bushing is tapered complementary to the tapered configuration of thesecond end of the connecting rod.
 22. The engine of claim 21, whereinthe bushing tapers from a lower portion to a top portion, and the topportion of the bushing has a width less than that of the lower portionof the bushing.
 23. The engine of claim 22, wherein the markings arepositioned along a circumference of the

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